That is the expected behaviour. It is explained here:
https://mantisbt.org/docs/master/en-US/Developers_Guide/html-desktop/#dev.plugins.building.properties

Probably, you can request to the plugin mantainer to update the plugin to support current mantis version.

From README of the plugin

Supports MantisBT v2.x (modern ui) -- use modern-ui branch

https://github.com/mantisbt-plugins/csv-import/tree/modern-ui

There you will find

$this->requires = array( 'MantisCore' => '2.0.0' );

and some more changes to make this plugin compatible to MantisBT 2.x.

Thank you both for your responses.

Just to make sure I'm understanding the use model in this situation, is it appropriate for me to manually update the $this->requires setting in the Csv_import.php file to accommodate our installation? Is that proper procedure for any plug-in for which the plugin may require by default a major release much older than a presently-available one (but for which the README may indicate a compatibility)? Or, is the developer guide information implying how the compatibility requirement needs to be updated by the plug-in owner in order to accommodate our MantisBT version?

Thanks,
Ryan.

We use semantic versioning for MantisBT, see http://semver.org

This means that MantisBT 2.x is a so called MAJOR version

MAJOR version when you make incompatible API changes,

Some 1.x plugins might work in 2.x without any changes, some plugins might need changes.
The Mantis core does not know what the old plugin is doing, so plugins requiring MantisCore 1.x are invalidated to prevent problems.

Sounds good. What I gather from this, then, is that I should contact the plug-in developer to determine if there is a donwloadable package for which the requires setting points to MAJOR version 2.x, or if the current one supports 2.x (in which case I'll ask if it's appropriate for me to hack the php file and update the requires setting manually).

Assuming I'm understanding the situation correctly, please feel free to close.

Thanks very much for the feedback.

Ryan.

or if the current one supports 2.x

Typo? 1.x?

contact the plug-in developer to determine if there is a donwloadable package for which the requires setting points to MAJOR version 2.x

@helfy022 Not sure the plugin's developer is needed... Just download the correct version of the source from
https://github.com/mantisbt-plugins/csv-import/archive/modern-ui.zip

Thank you very much. Confirmed that the MantisCore requirement is indeed 2.0.0 in the referenced package, thus addressing the noted dependency for the plug-in.

Another example of a plug-in for which the MantisCore requirement prevents out-of-the-box usage is Reminder:

https://github.com/mantisbt-plugins/Reminder/blob/master/Reminder.php:
$this->requires = array('MantisCore' => '1.3.0',);

The support page notes that a MantisBT issue should be filed against [Plugin - Reminder] for support requests. Should this issue be re-assigned to proceed with the related discussion on Reminder? Should a new issue be opened and "[Plugin - Reminder]" included in the Summary/Description?

Thanks,
Ryan.

Re-opening to inquire about next steps regarding Reminder plug-in.

Thanks,
Ryan.

The support page notes that a MantisBT issue should be filed against [Plugin - Reminder] for support requests.

So why are you reopening this then ? Just file a new issue under the appropriate project as indicated (click the link...)

Thanks for the clarification. I will proceed with the opening of a new issue against [Plugin - Reminder].

Please feel free to close.

Thanks again for all of the useful feedback.

Ryan.